There is accumulating evidence suggesting that free radical-mediated oxidative stress is implicated in the pathogenesis of diabetic neuropathy by inducing neurovascular defects that result in endoneurial hypoxia and subsequent nerve dysfunction. Administration of physiological antioxidants including thioctic acid, a potent lipophilic free radical scavenger, resulted in prevention of neurovascular abnormalities associated with experimental diabetic neuropathy providing the basis for a potential therapeutic value in diabetic patients. In a randomized double-blind placebo controlled dose-ranging study, an improvement in symptoms of dPNP during a 3-week period of intravenous treatment with 600 mg of thioctic acid per day, compared to placebo, has been demonstrated. A dose of 100 mg failed in this respect, whie a dose of 1200 mg, being efficacious in some of the parameters, was assoicated with a higher incidence of adverse events. Thus, the rationale for this study is to confirm the results reported by Ziegler with a dose of 600 mg.